In epidemiological studies relying upon respondents' retrospective reports of exposure or disease, recall bias is considered a threat to the validity of any substantive conclusions that can be made. It is said to occur when sensitivity and specificity in measuring prior exposures is different for cases and controls. To the extent that recall bias does occur, the scientific adequacy of the resource-efficient case control design is compromised. Thus, the current project intends to evaluate and identify research design conditions under which recall bias is most likely to occur. One phase of the investigation involves a comprehensive and systematic literature review of epidemiological studies proposing to test for the occurrence of recall bias. Whether one of several processes proposed to underly recall bias could plausibly explain the pattern of findings across studies will be explored. A second phase will involve analysis of data from a study including concurrent and retrospective reports of life events among chronic pain patients and controls, again focusing on identification of the cognitive processes underlying recall bias. The final project phase will consist of proposal preparation for conduct of a study designed to test more definitively the specific conditions under which recall bias is most likely to occur.